This invention relates to a method of integrating an internal combustion engine, an electrical machine, which can operate as a generator or a motor, a Rankine-type power cycle and an air conditioning and heating system to provide a self-contained, portable cooling, heating, and power system for an environmentally controlled space, such as a building, vehicle, or shelter.
Many industrial processes produce waste heat of low temperature, such that little useful work is generally accomplished with this waste heat. It is well known that certain thermodynamic cycles, such as absorption cooling, can provide environmental cooling even from low grade heat sources, such as thermal solar, engine exhaust, and bottoming cycles for industrial steam generators, but absorption cooling suffers from low efficiencies. In addition, cycles, such as absorption cooling, cannot easily integrate electrical power generation and do not lend themselves to compact and portable designs.
Prior art has not completely integrated heating and cooling with electrical power generation, or alternatively with an electric motor/generator to supplement the thermodynamic cycle with the electric motor during periods of low thermal energy availability. Furthermore, a self-contained system that includes a prime mover, such as an internal combustion engine, combined with power generation and heat and cooling functions, which are further supplemented by waste heat recovery from the engine exhaust have not been described. In the prior art, some systems use refrigerant as the working fluid to generate electrical power (Edwards, U.S. Pat. No. 4,738,111), commonly referred to as an Organic Rankine Cycle. Other systems provide for power and cooling, but use an external combustor, instead of an internal combustion engine (McCullough, U.S. Pat. No. 5,228,309). Many do not consider the need for recuperation, which transfers the remaining usable heat at the output of the Rankine expander to pre-heat fluid entering the heater or boiler.
Prior art for the apparatus that provides the heating and cooling functions have been well described elsewhere (Benson, U.S. Pat. No. 6,581,384). It can be summarized that none have maximized the efficiency achievable with a combined internal combustion engine, Rankine cycle and refrigeration cycle. Some approaches either do not recuperate heat from the working fluid (Steuart, U.S. Pat. No. 1,871,244) or do not recuperate heat in a fashion that maximizes the temperature of the working fluid entering the heating device (Brola, U.S. Pat. No. 4,118,934). Some systems attempt to only provide heating (Schafer, U.S. Pat. No. 4,271,679) or cooling (Horn, U.S. Pat. No. 2,875,589) but not both. Some add complexity by using separate working fluids for the power and heat pump cycles (Silvern, U.S. Pat. No. 3,153,442) (Schafer, U.S. Pat. No. 4,271,679) (Meckler, U.S. Pat. No. 4,024,908).
Hence, there is a need for a single system of sufficient efficiency and simplicity to make the manufacture and operation economically attractive. Since the intent of the system is to operate by recovery of heat from an integrated prime mover, the integrated power, heating and cooling system must be flexible enough to accommodate variable electrical and air conditioning loads and allow simple controls with a minimum of sensors and actuators.